Blasting cap



March 10, 1931. w. PRITCHARD, JR 1,795,440

BLASTING CAP Filed July 24, 1930 F/s. F76. 2.

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Patented Mar. 10, 1931 UNITED STATES PATENT OFFICE WILLIAM PRITCHARID, JR., 015 VILKES-BARRE, :PENNSYLVANIA, ASSIGNOR TO HER- CULES POWDER COMPANY, OF WILMINGTON, DELAWARE, A CORPORATION OF DELAWARE IBLAS'IING CAP Application filed July 24, 1930. Serial 1%. 470,270.

My invention relates to an improvement in blasting caps.

Blasting caps are, as is well known, used for initiating or detonating commercial explosives as, for example, dynamite, so-calle-d permissible explosives and the like, which are extensively used in connection with the mining of coal.

Blasting caps are constructed for firing through the medium of a fuse and for firing electrically, and while under proper handling they seldom fail to fire, there are a certain proportion of failures with the result that live caps are found in blasted material.

The presence of a live cap in coal presents a definite menace, since if it is carried, as is likely, to the consumer it will almost certainly be fired when the coal is used and will likely cause substantial damage due to the power of its explosive charge.

Now in accordance with my invention I provide a blasting cap having all the essential elements and advantages of the present caps, but so constructed as to insure that if it is not fired it will be separated from, for example, coal during the preparation of the coal for shipment from the mine.

The blasting cap in accordance with my invention comprises essentially a casing, containing any usual or desired explosive charge and fitted for firing electrically or through the medium of a fuse, the casing "being suitably weighted to have a specific gravity higher than coal so that if it fails to fire and is present in coal which is removed from a mine, it will be separated from the coal in the usual preparation thereof for shipment, as, for example, in jigs or washers, or by the Chance flotation process.

Having now indicated in a general way the nature and purpose of my invention, I will proceed to a detailed description thereof with reference to the accompanying drawing, in which I have illustrated a preferred embodiment and in which:

Figure 1 is a sectional view of a blasting cap of the type adapted to be fired by a fuse and embodying my invention.

Figure 2 is a sectional view of a blasting cap of the type adapted to be fired electrically and embodying my invention.

In the drawing a indicates a cap shell of usual construction in the lower end of which is placed a mass of lead or other heavy material 0. The material 0 is provided in quantity sufiicient to render the assembled cap definitely of higher specific gravity than coal and desirably will be of such a character as not to be corroded by the explosive charge 6, contained within the cap shell and which may be of any desired material or composition, as fulminate, a fulminate-chlorate mixture or the like.

Referring now more particularly to Figure 1, the cap shell on is of usual construction and contains at its low-er end, for example, about one half inch of lead, 0 above which is a suitable charge of fulminate-chlorate suitably pressed into the shell. The end of the shell shown in Figure l is open for the reception of a length of fuse which is inserted and crimped in the usual manner when the cap is used. If now the cap of Figure 1 fails to explode, for example, because of failure of F the fuse, it will, in due course, pass from the V mine with coal, its open end being plugged by the end of its fuse. However, when the coal prepared for shipment, for example, by pgging, washing, gravity separation, or the like, the cap, being weighted and of higher specific gravity than the coal, will readily separate from the coal and pass off with waste separated therefrom.

The cap illustrated in Figure 2 shows the application of my invention to a cap constructed for electrical firing through the medium of a pair of lead wires f adapted to be connected to a source of current, as a blasting machine, and extending through sealing plugs d, 6 into a suitable charge 5, the ends of the wires being connected by a fusible wire by the fusing of which the cap is fired. In the lower end of the shell a beneath the charge I) is placed a mass of lead 0. The cap illustrated in Figure 2, if it fails to fire, will be separated from coal in the same manner as described in reference to the cap illustrated in Figure 1, since the lead I) will render the cap definitely of higher specific gravity than coal.

It will now be appreciated that my invention primarily involves the provision of a blasting cap which is Weighted with any suitable material. andin any suitable manner so as to have a specificv gravity higher" than that of coal. It Will be'appreciated thatthe particular Weighting described herein and in- V volving Weighting; the cap at or adjacent one end thus rendering the cap end heavy and causing it to tend to assume an upright position in a jig or Washer While desirable is not essential since the object of my invention may be obtained by any suitable Weighting which will cause the cap as a Whole to have a specific gravity higher than that of coal. Further, it Willbe appreciated that my invention may be embodied in blasting caps of any desired structure and containing any desired charge.

What. I claim and desireto protect by Letters Patent is z- 1. A blasting cap including in combination a casing and a charge Within the easin-g, the cap being Weighted so as to have a specific gravity higher than that of coal.

2. A blasting cap including in combination a casing, a charge positionedwithin the casing'and a mass of metal supported by the casing, said mass: of metal being of a Weight such that the cap as a Whole will have a spe- V cific gravity higher than that of coal.

3 A blasting cap including in combination a casing, a. mass of metal positioned VWlthlll the casing ad acent one of its ends and a charge positioned within the casing.

4. A blasting cap including in combination a casing, a mass of lead positioned with in the casing adjacent: one of its ends and a charge. positioned Within the casing.

In testimony of which invention, I have hereunto set my hand at VVilkes-Barre, Pa, on this 18th day of July, 1930.

WILLIAM PRITGHARD, J R. 

